December 2010
December 2010 was an extremely cold month across the entirety of the British Isles. It was the second coldest December on record for the CET region with only December 1890 being colder at -0.8. whilst it was the coldest December on record for the UK and it was the second coldest month on record for the IMT, only January 1963 was colder at -1.6. All regions had their first month since February 1986 with a negative mean temperature. December had the most prevalent cold spell since February 1991 across the British Isles. The UK had their lowest December minimum temperatures since December 1995 with Altnaharra, Scotland dropping to -21.3c on the 2nd. January 2010's minimum was over 1.0c lower though at the same station with -22.3c on the 8th. Meanwhile, Ireland had their lowest December minimum temperatures on record. Straide, Co. Mayo recorded -17.5c on December 25th, the lowest December minimum ever recorded in the Republic of Ireland. -18.7c was recorded at Castlederg, Co. Tyrone on December 23rd, the lowest December minimum ever recorded in Ireland as a whole. Cavan, Co. Cavan recorded a maximum of -9.8c on December 21st, the lowest ever maximum on record for any month in the Republic of Ireland. Castlederg had a maximum of -11.0c on December 18th and Edenfel, Omagh, Co. Tyrone had a maximum of -11.3c on the 19th, both Ireland and Northern Ireland's lowest all-time maximum temperatures. Altnaharra recorded a maximum of only -15.8c on December 22nd, the lowest in the UK since December 1995. The month had two temporary mild spells, 9th-15th and the 27th-31st where temperatures rose to around average but still stayed below for some places where cloud was very persistent and fog took place. The UK's maximum for December was 12.0c at Treknow and Bude which are both in Cornwall, on the 28th whilst the overall maximum for December was 12.9c at Shannon Airport, Co. Clare in Ireland. Overall, the month had the highest number of days with air frost for December on record for the British Isles with a total of 23 days on average in the UK recording an air frost beating 21 days in December 1981. As to be expected with how cold the month was, December 2010 was a dry month. It was third driest December on record for the UK with only 47.5mm recorded - 40% of the 1981-2010 average. As can be seen from the December 2010 UK rainfall anomaly map, much of the UK was very dry with only a select few regions recording close to their average rainfall, most notably northeastern Scotland where low pressure was often centred during the month. The Republic of Ireland had 59% of its average December rainfall and it was the driest December since 2001 for some stations whilst for others, it was the driest on record. In contrast with December 1890 which was -0.1c cooler than December 2010, this month was mostly sunny. It was the sunniest December since 2001 or 2008 in the UK, the sunniest on record in Northern Ireland, the second sunniest on record for the Republic of Ireland and Scotland. Southeastern England had a dull month however with less than 50% of their average sunshine recorded. This distribution of anomalies was down to how the pattern was setup with low pressure concentrated on the eastern half of the UK. Day to Day Summary November 2010 ended on a very cold note bringing some of the lowest November temperatures ever recorded in the British Isles. This extreme cold would continue into the opening days of December with the majority of places struggling to get above freezing on the 1st and 2nd. Castlederg fell to -11.7c overnight into the 2nd. Altnaharra recorded a maximum of -14.0c on the 2nd. Snow showers affected many places with eastern England in particular on a strong bitter easterly airstream. Parts of Surrey and Sussex had snow accumulations of up to 25cm. Snow depths were up to 55cm at Westgate, England on the 2nd and 58cm at Balmoral, Scotland on the 1st. RAF Leeming in North Yorkshire had a minimum of -17.9c on the 2nd, its lowest temperature on record since its records began in 1945. The snow showers cleared on the 3rd leaving the country in a widespread severe frost and many places recording dense fog leading to poor visibility. Redesdale Camp, Northumberland, England got down to -19.5c on the morning of the 3rd. Sennybridge, Powys, Wales fell to -12.9c. At the same time, a band of rain, sleet and snow moved southeastwards during the day. Another very cold day with maximums struggling around -2 to 2c widely. Braemar, Scotland got down to -20.4c on the 3rd. Mount Juliet, Kilkenny woke up to a minimum of -16.4c on the morning of this day. Not as frosty as previous nights into the 4th with minimums staying up to -7 to -2c generally. The 4th was a milder day too with maximums of 0-6c. It was much milder in the south due to some rain trying to push up from the Bay of Biscay whilst elsewhere there were scattered rain and wintry showers. This rain pushed into the southeast of England overnight before clearing on the 5th. Behind the rain, there was clear skies bringing severe frost and ice and temperatures getting back down below -5c widely. Any showers that pushed into this cold air turned into snow but the snow was very isolated. It was a sunny day on the 5th and the sun made it feel even colder with the exception of the southwest. Maximums similar to the 4th of 0-6c. A cold front pushed down from the north overnight into the 6th but even before the front pushes southwards, still very cold with parts of the Pennines getting down to -10c or less. Topcliffe got down to -18.0c early on the 6th. This front continued to move further south on the 6th and 7th bringing some heavy snow of up to 10cm in any parts affected by it but becoming weaker as it eventually reaches the milder air to the extreme south. As it cleared on the 7th, further snow showers pushed down from the north in a bitter northerly airstream. Temperatures struggling to get above freezing especially in those locations with the snowfall. Church Fenton had a maximum of only -6.8c on the the 6th, Scampton had a maximum of only -5.6c on the 7th. Northerly winds continued into the 8th with snow showers to the north and east and some rain to the extreme southeast but mostly sunny and cold across the board with maximums struggling again around -6 to 4c. Some places were even lower than this range though as was Carlisle where they had a maximum of only -7.9c on the 8th. The northerly airflow starts to become a northwesterly on the 9th as high pressure starts to come closer to the UK than over Greenland. With this, came some milder air and a lot of cloud off the Atlantic. There was still some light flurries scattered over northern England and southern Scotland. Generally it was milder though with maximums in the 1-7c range. Frost became far less severe with the northwesterly air stream due to the increasing amounts of cloud. In fact, the 10th was a very damp day with some drizzle up to the north spreading southwards but pretty uneventful with overcast conditions and temperatures widely up to 6-8c. Some places struggled though around 3-4c in fog. The maximum temperature got up to 10.1c at Drumnadrochit on the 10th in fairly strong winds. Derrylin reached 9.3c at the same time. These parts hadn't seen these kinds of temperatures since the middle of November. High pressure of over 1030mb sat over Ireland on the 11th before ridging in over top of all the British Isles on the 12th with winds becoming more slack allowing frost to develop. The showers cleared southern regions and the sun appeared for many; the exception being the north of Scotland where it was overcast close to the centre of the high pressure. It was a colder day generally as a result in maximums around 4-6c, the same continued into the 12th. However, parts of the west were fairly mild. For instance, Stormont Castle got up to 9.6c on the 11th. Both nights were quite cold with a minimum of -4.8c at Eskdalemuir and Tyndrum early on the 12th. A weak stationary front pushed southwards down the east of the UK from the 13th into the 14th and brought some drizzle or light rain here, particularly in East Anglia on the 14th before it cleared on the 15th. Some sunny spells out to the west on the 13th and 14th, more so for the west of Ireland but otherwise rather overcast with high pressure close to us up to the northwest. Fairly cold on the 13th especially in the sunny spells with maximums of 2-6c and similar temperatures on the 14th. The 15th was a rather dry and dull day with temperatures rising a bit to the likes of 4-7c in most places so near normal for the time of year. Patches of fog scattered in Scotland and Ireland. The winds started to become a northerly on the 16th bringing cold air straight down from the Arctic. A monster block of high pressure came over Greenland with a central pressure of up to 1075mb on the 15th. The cold air came in behind quite an active cold front which brought a band of rain southwards. Behind it, temperatures plunged very fast as did snowfalls develop widely across the north. Maximums up to 8c in the south ahead of the front but already down to -1c in parts of northern Scotland. Minimums already getting down to -7.8c at Sennybridge, Wales overnight the 16th into the 17th. A severe cold spell had set in bringing the coldest weather in Ireland since January 1982 in terms of minimum temperatures and since January 1987 in terms of maximum temperatures, colder than anything the previous spell at the end of November and start of December brought. To have two severe cold spells to this extreme in the same month is unprecedented and absolutely incredible. Strong northerly winds on the 17th brought plenty of snow showers, particularly Northern Ireland where accumulations of 10-15cm were quite widespread with up to 20cm in the east, and bitterly cold temperatures with daytime maximums widely between -1 to 2c. The crisp Winter sunshine did not help at all in making the temperatures rise above freezing. Loch Glascarnoch, Scotland got down to -17.2c overnight into the 18th. A low pushed into England and Wales on the 18th which would initially bring some heavy rain if it were not for the cold air but the air was so cold, it made all the rain turn to snow bringing snow accumulations of up to 10-15cm here. Elsewhere, there was scattered snow showers with some heavy ones to the north of Scotland but otherwise extremely cold with sunny spells as the winds veered more to a northeasterly than a direct northerly that had began on the 16th. This northeasterly would stay for quite a few days before high pressure started to ridge in from the north and west towards Christmas time. Castlederg, Northern Ireland had a maximum of -11.0c on the 18th, this was a new record for Northern Ireland; not just for December but for any month and this record would be beaten again nearly a week later. A minimum of -19.6c at Shawbury, -18.7c at Pershore, both in England and -12.2c at Llysdinam, Wales overnight into the 19th. Further snow showers occurred in the north of the UK as well as parts of Ireland on the 19th especially to the east of Scotland where they recorded more accumulations of up to 15-20cm. Plenty of sunshine and icy conditions with temperatures continuing to be well below freezing otherwise. Low pressure pushed into the southwest of Ireland, initially rain at first, went into the southwest of the UK and travelled northwards through the morning into the afternoon of the 20th. This brought some heavy snow to the east of Ireland, Wales, the southwest and midlands of England. Accumulations of 10-15cm generally, perhaps more locally. Capel Curig, Wales had a maximum of -8.6c on the 20th after an overnight minimum temperature of -17.5c. Minimums of -11.9c at Blackpool and -10.5c at Scarborough were recorded overnight into the 21st. The low lost its energy and became an area of cloud in England on the 21st bringing temperatures above freezing here with maximums potentially reaching 4c. This was in huge contrast to the north and west where temperatures were well below freezing again and Irish Sea streamers set up to the east of Ireland. Streamers have huge variability on where the snow is likely to occur but if you were not in the shadows of the Isle of Man or Anglesey, you got plenty of snow of up to 20cm accumulations on the 21st added from 10-15cm on the 20th. Some scattered snow showers to the north and west of Ireland too but not as heavy as these streamers. Oak Park, Co. Carlow had snow depths around 30cm. Sunshine elsewhere. Ballyhaise failed to get above -9.4c on the 21st whilst Cavan failed to get above -9.8c. The streamers continued into the 22nd with another 10-15cm accumulations really adding to disruption. An area of snow developed over England after it pushed up from the English Channel on this day and brought a good 5-10cm just to the south of Manchester during the morning hours. Altnaharra, Scotland recorded a minimum of -20.2c in the morning of this day rising to a maximum of only -15.8c, just 0.1c short of the UK's record low maximum of -15.9c set at Fyvie Castle on 29 December 1995. Some flurries to the east of England and north of Scotland on the 23rd, heavier in the extreme southeast corner close to a low over France. Temperatures were above freezing in these showers but the windchill made it feel absolutely bitter. Besides the Irish Sea streamers bringing some more heavy snow to the east of Ireland of another 10-20cm, it was a very cold and sunny day though cloudy to the south of England. Castlederg set a record low for Northern Ireland of -18.7c on this day and Edenfel, also in Northern Ireland, broke the Castlederg minimum record set on the 18th with a daytime maximum of -11.3c on the 23rd. Machrihanish, Scotland got down to -12.9c overnight into the 24th The snow showers generally dissipated on Christmas Eve, the exceptions being some parts of the northeast of England and the northwest of Scotland, as high pressure approached from the west to give a very sunny and cold day across the entire country which would continue on into Christmas Day. There was a low to the northwest of Scotland which brought some snowfalls of up to 10cm and some freezing rain close to the coasts. This brought a white Christmas for them. However, elsewhere, no snow fell during the 24 hour period of December 25th which meant it wasn't an official white Christmas going by the definition. On the other side, 83% of the UK stations recorded lying snow at 9am on Christmas morning meaning it was the whitest Christmas on record using this, records going back to the 1880s. The debate lies then on if 2010 should be regarded as a white Christmas or not because as the definition states, one snowflake has to fall within the 24 hour period of December 25th for a white Christmas to be official. There was plenty of sunshine to be enjoyed across the board, at least for most, with high pressure over top of us but daytime temperatures were very low and for some, record breakingly so. In fact, it was the equal sunniest Christmas on record with 1979 with Cornwall recording a daily sunshine of 7.5 hours. Llysdinam got down to -16.5c on Christmas Day. Pershore fell to a minimum of -16.2c on Christmas night to a maximum of -6.4c on the 26th. Casement Aerodrome had a minimum of -15.7c on Christmas morning which was the lowest temperature on record in county Dublin. It was the coldest Christmas Day for the CET since 1830 with a mean of -5.9c. The start of the 26th brought further widespread frost and ice with temperatures again well below freezing. Castlederg was down to -14.6c whilst Exeter, England got down to -16.5c (The night of 26th/27th had a minimum of 4.1c here). However, cloud quickly approached from the Atlantic in Ireland ahead of some heavy rain pushing into here. Valentia Observatory had a daily rainfall of 49.2mm on the 26th and another 20.1mm on the 27th. Daytime temperatures in parts of Ireland and Scotland rose above freezing for the first time in over a week. This rain quickly melted all the snow in parts of Ireland so flooding became a concern for some though the thaw was far slower in the UK. Ice also became a huge problem in Ireland and Scotland as ground temperatures were still very cold. Serious water shortages were ensued as a result of the thaw causing pipes to burst. This rain pushed into the UK where the cold air lied and brought 2-10cm of snow across mid-Scotland and the Pennines. This warm front lost its energy through the afternoon of the 27th before another front pushed up from the southwest and brought more rain over Ireland and the west of the UK. As this reached the midlands of England overnight into the 28th, the rain turned to snow but only for a few hours because the mild air won the battle and any snow that fell became slush fast. Some rain showers to the northwest of Ireland and drizzle to the south of the UK. Temperatures reaching double figures here as well as parts of the south of Ireland, for the first time in over a month. For quite a few places though, they did not reach 10c all month. Most rain showers cleared on the 29th but it was overcast with some patches of fog and mist scattered about. This continued on into the 30th and New Year's Eve with sunshine being a hard element to spot. It was a very uneventful end to what was the most remarkable December you could find cold and snow wise. Think farmers though were happy for it to be uneventful given the challenges they had suffered in the past month. Temperatures paid back a touch on the 30th and 31st down to single figures again around 5-7c generally. Forecasting In Autumn 2010, Polish meteorologists began predicting that 2010-11 would be the coldest in Europe in a thousand years. Citing the lower flow speed of the Gulf Stream, resulting in less warm water and less warm air being carried to Europe, they forecast that temperatures during January and February would fall as low as -30c across much of Europe and remain there for weeks on end. After sharp frosts on the 16th October which was before the official end of British Summer Time, agencies had thought then that the Polish meteorologists might have been on to something. The UK Met Office had hinted at the potential for a cold spell to take place at the end of November 2010, in their 30 day forecast at the beginning of the month. M.T. Cranium of Boards.ie had forecasted the cold spells very accurately from the Autumn and even nicknamed them the Greenland Express which he is now known on Boards.ie for. Here's some examples of his forecasts: Outlook on 12 December 2010 I continue to look at the situation this way (after reviewing 12z runs) ... the basic picture is that very cold air arrives very rapidly on Thursday, settles in for several if not many days, and a frontal battleground develops to the south of Ireland. At this stage, can't ask for much more than that if you're a snow fancier. The details are bound to be murky for several days yet. I noticed the BOM model getting a boost earlier, it happens that the GEM (Cdn) model is also showing a winter storm at day 6. The GFS is moderately positive for snow, the ECM has the strangest looking evolution that would be good for snow if shifted perhaps more realistically to a southwest track for the energy, and the UKMO has the best setup for continuing cold. Having in the back of my mind this energy peak for 20-21 Dec, I believe this could all fall into place with the cold air locked in, then a storm tries to push back from a position near 50N 20W, somewhat similar to last year's full moon end of December storm (the dates shift forward by ten days a year with lunar analogues). If you recall, that storm pushed mild air into the south, gave a heavy rainfall, then backed off and the precip turned to sleet and then snow before much colder air returned. This time around, we seem to have deeper cold air in place before the event. This is why I figure it could turn into a snowstorm if there are similar dynamics. Dealing with the more certain forecast first, though, we need to stress that cold and locally heavy snow will arrive very rapidly Thursday, and wintry weather will become a problem for the north as early as mid-day Thursday -- will be considering an alert for the Monday morning forecast here, as we have plenty of time, but on the current model consensus, could see 5-10 cm snowfalls in parts of Ulster and inland Connacht on Thursday. This is basically a Greenland express coming down the line on 30-50 mph winds (the remnant of 50-70 mph winds further north around Jan Mayen). The speed of development is truly staggering with this -- far to the north, conditions change within 24 hours from almost calm to hurricane force winds as the gradient suddenly increases. The Greenland high reaches values into the 1075 mb range with a 980 mb low not that far away west of Svalbard. This is a huge pressure differential and will accelerate the southward charge of arctic air. The thing that looks wonky to me on the models is how this low transfers west so effortlessly when the evolution seems to call for low pressure formation in the North Sea. I'm wondering if the missing link is that pressures may rise faster from northwest Russia across Norway late in the week and clamp down on the whole complex of low pressure -- watch for that tendency in later model runs. Outlook on the 13 December 2010 This may tend to look like just a dry northerly with local wintry showers, but the depth of cold air in this "Greenland express" is the deal maker, and the transfer of the polar vortex southwest across Ireland towards Kerry is likely to turn the wind flow around into more of a southeast or easterly flow by Sunday ... so the main dynamics of this cold spell are likely to be (a) initial blast of sudden cold, locally heavy snow in north and west, but some brief squally showers elsewhere (Thursday into early Friday) (b) settling in of deep cold aided by new snow cover, slack winds, clearing skies, and feed from very cold pockets over Britain, possibly giving severe minimum temps (below -12 C) by Saturday morning ... this may continue in the north into Sunday morning. © possible snowfall events of moderate or even heavy amounts, affecting the south and east, as lows form to the south of Ireland and interact with the deep cold in place. Could also state that the GFS model has been almost routinely losing the plot after 6-8 days with its tendency to allow spurious mild rebounds from the southwest courtesy of deep lows that end up being much further south at event time. In other words, any depictions of sudden breakdowns and thaws have to be treated with caution. Sooner or later, one will happen (the recent mini-thaw was more of an anticylonic interval that was a necessary step in building up the Greenland block). Looking back at past "severe" or epochal type winters, the Greenland high tends to become semi-permanent so we have to factor in that with these synoptics, there has to be a reasonable chance of a long-lasting cold spell. There is even colder air waiting in parts of Russia to move towards Scandinavia and add a bitter continental feed to the mix, and then the North Sea is chilling rapidly thanks to the outpouring of near-freezing water from the Baltic and from rivers running into the North Sea. All the building blocks are in place for some very severe winter weather. Any sort of responsible probability analysis would say that the chances of disruption from snow in Ireland and the southern U.K. must be higher than normal by a factor of five or even ten to one. But there is nothing quite carved in stone yet. I think the period Sunday to Tuesday is very likely to see snow in parts of Ireland, let's leave it at that for now. Potential amounts would range from slight to very considerable, won't speculate with numbers. Statistics Record low minima for each date of December in the UK Gallery ' SnowSheffield1dec10.jpg|Snow falling in Sheffield on 1 December Original.jpg|A tunnel of snow covered trees at Hillborough on 3 December 8500554315_78d3971edd_c.jpg|Snow on O'Connell Street, Dublin on 21 December Cabhair_swim_2010_big_freeze.jpg|CABHAIR swim at Inchicore, Dublin on 25 December Original_%281%29.jpg|Grand Canal in Dublin frozen on 3 December DWJw5_bXcAAS5Wn.jpg|Nass on 22 December 00-DSC04541.jpg|Raford, Galway in the snow on 18 December 35849590874_9739805a4f_o.jpg|Ashtown train station on 1 December ' References # UK Met Office December 2010 climate summary # UK Met Office November/December 2010 cold spells past event article #TheDailyEdge 4th year anniversary article of December 2010 #Winter 2010-11 in Great Britain & Ireland wikipedia #Trevor Harley's 2010 analysis #KildareWeather's 22 December picture #Raford, Galway 18 December pictures